Generally in an ordinary telephone, when the user who has finished a call replaces the receiver on the cradle of the telephone, a hook switch is automatically actuated by the weight of the receiver and the telephone is consequently set in a standby state waiting for the next incoming or outgoing call.
In the case of a cordless telephone, namely a telephone relying upon radio communication connection between the main unit or base unit (hereinafter referred to as "base unit") of the telephone and a handset or portable unit corresponding to the receiver portion (hereinafter referred to as "portable unit") of the telephone, which has begun to find popular acceptance particularly in the United States, since the functions for reception, transmission, and dialing are incorporated on the portable unit side and in order that the telephone may resume the standby state without requiring the portable unit to be placed on the cradle of the base unit at the termination of each call, a "service"--"wait" changeover switch which is equivalent to the hook switch of the ordinary telephone is provided on the portable unit side so as to be manually operated.
Because of the construction described above, with the cordless telephone there is a possibility that even if the user adheres to the practice of replacing the portable unit on the cradle of the base unit at the end of each call, he will at times forget to turn the "service"--"wait" changeover switch to the "wait" side. If this happens, the service circuit will remain in its connected state and, particularly, the transmission circuit will continue not merely to operate uselessly but also to transmit unnecessary electric waves possibly to affect adversely other communication paths.
To avoid this situation, there has been proposed a device which, similar to the concept of the hook switch in the ordinary telephone, utilizes the impact of replacement of the portable unit on the cradle of the base unit to operate the changeover switch by means of a mechanical actuator and set the telephone to the standby state. By this measure, however, the size and appearance of the base unit and the portable unit and the layout of their component parts must be designed all over again specifically to permit incorporation of the additional function. No minor modification to the conventional cordless telephone suffices for the desired incorporation of this additional function. Thus, the proposed device lacks adaptability. Further, it inevitably entails an increase in a loss of the number of mechanical parts and, therefore, reliability.